1. Field of the Invention
The present invention relates to a magnet roller for use as a magnetic brush development roller e.g., for a copying machine, a laser beam printer, or other printing apparatus. The roller is formed of a resin magnetic material, and is; provided with a plurality of magnetic pole pairs in which the surface magnetic flux density of at least one of the magnetic pole pairs is different from the of the others. The present invention also relates to; a method for manufacturing such a magnet roller and to manufacturing apparatus there for.
Also, the present invention relates to a development unit provided with said magnet roller and a copying apparatus provided with such development unit.
2. Related Background Art
Traditionally, a magnet roller manufacturing method of this kind is one such that a plurality of fan-shaped roller pieces each having magnetic pole pairs are formed in advance so that the magnetic flux density of at least one of the magnetic pole pairs is different from that of the other pairs, and hose roller pieces are connected with each other by adhesive or the like, thereby producing a magnet roller having a plurality of the magnetic pole pairs in which the surface magnetic flux density of at least one of the magnetic pole pairs is different from that of the others.
This magnet roller is mounted in the development ring (sleeve) for use in a conventional development unit having toner arranged around it.
The conventional magnet roller described above has drawbacks in that the dimensional precision and configurational precision of the magnet roller are low since the magnet roller is obtained by connecting a plurality of roller pieces which are prepared individually in advance, and in that the magnetic characteristic eventually deteriorates due to ripples in the magnetic poles.
Also, this magnet roller manufacturing method has a drawback in that productivity is low due to its complicated manufacturing processes.
There is further a drawback in that a development unit (developing machine) provided with such a magnet roller can not control the thickness of the toner or the density of the developed image within a specified range, thus lowering the quality of the developed image. Accordingly, a copying apparatus provided with such a developing machine will inevitably have a drawback in that the quality of its copied image is degraded.